Oxidoreductase IruO in the oxidized form

Experimental Data Snapshot

  • Resolution: 2.31 Å
  • R-Value Free: 0.207 
  • R-Value Work: 0.183 
  • R-Value Observed: 0.184 

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Iron Uptake Oxidoreductase (IruO) Uses a Flavin Adenine Dinucleotide Semiquinone Intermediate for Iron-Siderophore Reduction.

Kobylarz, M.J.Heieis, G.A.Loutet, S.A.Murphy, M.E.P.

(2017) ACS Chem Biol 12: 1778-1786

  • DOI: https://doi.org/10.1021/acschembio.7b00203
  • Primary Citation of Related Structures:  
    5TWB, 5TWC

  • PubMed Abstract: 

    Many pathogenic bacteria including Staphylococcus aureus use iron-chelating siderophores to acquire iron. Iron uptake oxidoreductase (IruO), a flavin adenine dinucleotide (FAD)-containing nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reductase from S. aureus, functions as a reductase for IsdG and IsdI, two paralogous heme degrading enzymes. Also, the gene encoding for IruO was shown to be required for growth of S. aureus on hydroxamate siderophores as a sole iron source. Here, we show that IruO binds the hydroxamate-type siderophores desferrioxamine B and ferrichrome A with low micromolar affinity and in the presence of NADPH, Fe(II) was released. Steady-state kinetics of Fe(II) release provides k cat /K m values in the range of 600 to 7000 M -1 s -1 for these siderophores supporting a role for IruO as a siderophore reductase in iron utilization. Crystal structures of IruO were solved in two distinct conformational states mediated by the formation of an intramolecular disulfide bond. A putative siderophore binding site was identified adjacent to the FAD cofactor. This site is partly occluded in the oxidized IruO structure consistent with this form being less active than reduced IruO. This reduction in activity could have a physiological role to limit iron release under oxidative stress conditions. Visible spectroscopy of anaerobically reduced IruO showed that the reaction proceeds by a single electron transfer mechanism through an FAD semiquinone intermediate. From the data, a model for single electron siderophore reduction by IruO using NADPH is described.

  • Organizational Affiliation

    The Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia , Vancouver, British Columbia V6T 1Z3; Canada.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Ferredoxin--NADP reductase344Staphylococcus aureus subsp. aureus USA300Mutation(s): 0 
Gene Names: SAUSA300_2319
Find proteins for Q2FEC4 (Staphylococcus aureus (strain USA300))
Explore Q2FEC4 
Go to UniProtKB:  Q2FEC4
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ2FEC4
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on FAD

Download Ideal Coordinates CCD File 
C27 H33 N9 O15 P2
Experimental Data & Validation

Experimental Data

  • Resolution: 2.31 Å
  • R-Value Free: 0.207 
  • R-Value Work: 0.183 
  • R-Value Observed: 0.184 
  • Space Group: P 41 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 90.591α = 90
b = 90.591β = 90
c = 138.537γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XDSdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Canadian Institutes of Health Research (CIHR)CanadaMOP-102596

Revision History  (Full details and data files)

  • Version 1.0: 2017-10-04
    Type: Initial release
  • Version 1.1: 2020-01-08
    Changes: Author supporting evidence